1. Field of the Invention
The present invention relates to a shredding device which is incorporated in a filter attachment designed to connect cigarettes and filters and which shreds a paper web to produce paper pieces used for connecting cigarettes and filters.
2.Description of Related Art
This type of filter attachment is provided with a non-contact shredding device which is disclosed in the publication of examined Jp patent application No. S61-54559. This publicly known shredding device includes a receiving drum and a bladed drum. The bladed drum has a plurality of shredding blades arranged equidistantly on the peripheral surface thereof and a pair of free rollers installed on both ends. These free rollers have larger diameters than that of the bladed drum and they are rotated while being contact with the receiving drum.
With the receiving drum and the bladed drum being rotated in the opposite direction from each other, a paper web is supplied between the receiving drum and the bladed drum. When the paper web passes through these drums, the shredding blades of the bladed drum shred the paper web into paper pieces of a specified length without contacting the peripheral surface of the receiving drum.
Thus, the shredding blades of the bladed drum do not collide with the receiving drum at the time of shredding the paper web, making it possible to prevent shredding noises caused by such a collision and also to prevent damages to the receiving drum or the shredding blades.
In the non-contact shredding device described above, the shredding performance heavily depends on the size of the gap between the shredding blades and the receiving drum when the shredding blades approach most closely to the peripheral surface of the receiving drum. For this reason, the gap must be maintained at a constant dimension to maintain the desired shredding performance.
In recent years, the required rotational speed of the receiving drum and the bladed drum is increasing with increasing operation speed of the filter attachment. As the rotational speed of the drums increases, the free rollers, which rotate in contact with the receiving drum at all times, tend to overheat due to frictional heat. When the temperature of the free rollers rises, the outside diameters of the free rollers increase due to thermal expansion. As a result, the foregoing gap increases, preventing the shredding blades from reliably shredding the paper web.